Not Applicable.
Not Applicable.
1. Field of the Invention
This invention relates to knives with retractable safety sheaths or hoods.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
This invention provides improvements in knives with retractable hoods. This invention provides a knife with a retractable hood with improved durability, reliability, and with a hood that provides enhanced safety and which automatically locks in the closed position.
U.S. Pat. No. 2,376,887 discloses two embodiments of a package cutter having a pivoting mounted guard which covers exposed parts of the blade. The guard has two rearwardly projecting ears, one of which has an opening through which a pivot member is engaged and also has a spring which engages the pivot member and urges the guard to a blade covering position.
U.S. Pat. No. 2,370,800 discloses a safety paper box cutter having a razor blade inserted through an opening of the body where the blade is retained bearing against a body end wall. The guard member is pivoted near the end of the body and is yieldingly held in the operating position by the spring.
U.S. Pat. No. 2,743,523 discloses a carton opening knife with a razor blade which fits into a horizontally extending recess and is secured by a clip member having a run which contains the blade within the confines of the clip member when the clip is in repose.
U.S. Pat. No. 3,781,988 discloses a safety paper carton opening blade holder in which a blade is retained by fingers and a guard is mounted on pivot trunnions above the blade. The guard is biased in a closed position by a spring.
U.S. Pat. No. 4,531,286 discloses a carton cutting knife in which a razor blade is retained by detent means on the blade mounting extension and a blade guard is secured to the knife by a flexible attachment strap.
U.S. Pat. No. 4,744,146 discloses an adjustable-blade safety knife with carton-cutting guide in which the blade is slidably-retained within the handle in the closed position and extends from the end of the handle in the open position and having a guide which constrains the blade to cut the side of the carton at a slightly inclined angle from the horizontal.
U.S. Pat. No. 4,899,443 discloses a safety knife for cardboard with a longitudinally slidable knife blade holder spring-loaded in the direction of the knife handle. The normally retracted blade is extended for use by using a finger to slide a guide within an elongated passage in the blade holder until a stop is encountered.
U.S. Pat. No. 5,241,750 discloses a utility razor safety knife with a normally closed hood which automatically self-locks in the closed position after use without action or adjustment by the operator. It is stabilized in its movement and biased toward the closed position by a yoke with springs attached. The disclosures of this patent are hereby incorporated by reference into this patent application.
U.S. Pat. No. 5,943,780 discloses a cutter for fibrous compressible material such as insulation batting. The cutter has an elongated base with a slot for the blade which normally prevents exposure of the blade but which is depressed by contact with material to be cut and allows the blade to protrude through the slot. A safety bar prevents movement of the base unless the cutter is gripped by the user.
The prior art inventions do not provide a safety knife with the reliable, durable, adjustable and efficient safety features of the present invention.
This invention is an improved safety utility razor knife of the type having a handle, a blade attached to the handle, a blade guard hood pivotally attached to the handle, the blade guard hood normally locked in the closed position by a locking plunger which is normally biased by a spring in the closed position. The locking plunger is released by a slide pushed forward from its resting position. Once a cut has been made and the cutter is lifted from the cut surface, the pressure dependent hood moves into the closed position and is automatically locked in that position by the locking plunger, regardless of the position of the slide. In order to move the hood to the open position and to cut again, the slide must be released and allowed to move to the closed, resting, position, then pushed forward into the open position, thereby unlocking the hood and allowing exposure of the blade and use of the knife.
Such knives are used for cutting paper box cartons, opening packages, cutting sheet materials such as roofing and floor coverings and removing insulation from coated wires.
The knife of this invention has the advantage of a xe2x80x9cnormally lockedxe2x80x9d hood, which insures that a knife which is not in actual use is in the safe configuration where the protective hood is locked in the closed protective position without any action on the part of the user or carrier.
In the present invention the hood is biased in the closed position by a hood plunger pin which is urged by a spring to hold the hood in the closed position, thereby preventing exposure of the blade. A slide which is biased by a spring in the closed position retains the hood plunger pin in the closed position and retains the hood in the locked position. In addition, a locking plunger is normally biased in the locked position and provides a mechanism for locking the hood in the locked position.
When it is desired to allow the hood to pivot upward with the exposure of the knife blade, the slide is pressed forward thereby allowing upward movement of the hood plunger pin into a groove in the slide. The upper surface of the groove slopes upward from the front to the back of the slide, thus allowing full upward movement of the hood plunger pin and full exposure of the knife blade when the slide is pressed fully into the forward position. In addition, pushing the slide forward causes the locking plunger to move backward, releasing the hood from the locked position. Completion of a cut and release of the knife from the cut surface allows the hood to snap into the closed position where it is immediately locked in the closed position by the locking plunger. This occurs despite the fact that the slide may be held in the forward position. The slide must be released and allowed to returned to the rearmost locked position and then pushed forward before the hood may be moved to the open position. This is an important safety feature which prevents injury associated with rapid cutting.
Release of the slide by the knife user allows the slide to move immediately to the rear locked position with the positive locking of the hood in the closed position by both the hood plunger and by the locking plunger. The knife now can be used by pressing the slide forward to the open position and pressing the hood against the surface to be cut. The hood now is free to pivot, exposing the edge of the blade.
In a second embodiment of the safety knife, the degree of retraction of the hood, and therefore the depth of cut of the blade, may be adjusted.
It is an object of this invention to provide a safety knife having a number of different safety hood embodiments adopted for specific cutting tasks.
It is an object of this invention to provide a safety knife wherein the retractable hood can be opened only by moving the slide from the closed position to the open position and pressing the hood against a surface to be cut, while the hood locks in the closed position when the knife is lifted from the cut surface regardless of the position of the slide.
It is a further object of this invention to provide a safety knife wherein the blade is positively protected against exposure without the necessity of any action by the user.
It is a further object of this invention to provide a safety knife wherein the hood is retained in the closed position by a positive locking mechanism and by a spring biasing the hood in the closed position.
It is a further object of this invention to provide a safety knife wherein the hood is automatically locked in the closed position when the knife is lifted from the cut surface, whether the slide is in the open position or closed position.
It is a further object of this invention to provide a safety knife wherein the biasing tension of the hood is adjustable.
It is a further object of this invention to provide a safety knife wherein action by the user is required in order to allow exposure of the blade, thereby preventing accidental injury by the blade.
It is a further object of this invention to provide a safety knife wherein the hood is transparent, thereby affording an improved view of the cutting surface for the user.
It is a further object of this invention to provide a safety knife which is stabilized against tilting when resting on a surface.
It is a further object of this invention to provide a safety knife wherein the hood accommodates a cable for use in slitting cable insulation.
It is a further object of this invention to provide a safety knife which is stabilized to ensure a right-angle cut.
It is a further object of this invention to provide a safety knife with an easily replaceable blade.
It is a further object of this invention to provide a safety knife having a grip contoured to insure a firm grip by each finger of the gripping hand, thereby preventing slipping of the knife when in use.
It is a further object of this invention to provide a safety knife wherein the amount of retraction of the hood, and thus the depth of the cut, may be controlled.
It is a further object of this invention to provide a safety knife wherein the movement of the safety slide is stabilized by a rocker pin.
It is a final objective of this invention to provide a safety knife which is safe, effective, reliable, durable, and inexpensive to manufacture without adverse effects on the environment.